In a message dated 3/4/2003 9:21:38 PM US Mountain Standard Time,
jimlux@earthlink.net writes:
> Indeed, it looks like a standard industry spec. But I was wondering why
> they selected that? And, is it aimed at 50-150 foot towers or 1000 ft
> behemoths.. For all we know, the EIA standard said that because it
> "seemed
> like a good number" and "it was in some other spec we had that seemed to
> work". Or, they may have had some independent analysis to back it up.
>
> Some background.... In my job at Jet Propulsion Lab, I deal with all manner
> of specifications, and, in the context of the ever pressing schedule,
> sometimes specs get in because they just got copied from somewhere else,
> without any backup for why that spec existed in the first place. The scary
> thing is that the original spec (7 or 8 generations back) may have been
> written as a "let's see what the prospective bidders will say" kind of
> requirement; or, perhaps, in that previous project, "cost is no object";
> or,
> maybe they wound up writing a waiver against an impossible requirement (but
> never went back and modified the spec).
>
>
I understand what you are saying, Jim. I am a Registered PE in several
states, since 1977, but not in the structural field. So I certainly
understand how specs can go back several generations and, if not quiestioned,
they remain current. My email was only meant to quote the standard and
evaluate the "go/no go" question that was on the table re that Rohn 55,
allgedly 12" out of plumb. I know nothing of how the standards' parameters
were derived nor the possible "politics". It's clearly out of my field of
expertise. I do know enough to attempt to satisfy most standards when
building my own station..... And "attempt" is a sometimes very accurate, hi.
I too would like to know how the 1 part in 400 spec originated.
73,Bob K8IA
Mesa, Arizona USA
near the Superstition Mtns
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